Constant voltage source



FIP821Z Sept. 27, 1949. H. E. KALLMANN CONSTANT VOLTAGE SOURCE Filed April 6, 1946 IN VEN TOR.

Patented Sept. 27, 1949 UNITED STATES PATENT OFFICE CONSTANT VOLTAGE SOURCE Heinz E. Kallmann, New York, N. Y.

Application April 6, 1946, Serial No. 660,267

13 Claims.

My present invention relates to electrical arrangements and more particularly to electrical arrangements adapted to serve as source of constant voltage.

It is an object of m present invention to provide a fixed or adjustable constant voltage source.

Another object of my present invention consists in a device adapted to serve as constant volt age source for loads with very high impedance.

A further object of m present invention consists in a device for comparing and measuring the light absorption of'translucent materials unaffected by the variations of the light source illuminating these materials.

Still another object of my present invention consists in an arrangement which is adapted to serve as a source of constant grid bias for amplifier and similar tubes.

With the above objects in view, my present 1n vention mainly consists of an electrical arrangement comprising in combination a source of activating energy, and two electrical elements each of which is activated by this source of activating energy and has a logarithmic voltage characteristic so as to yield during activation an individual output voltage the voltage variations of which in case of intensity variations of the above mentioned activating energy are in logarithmic proportion with the intensity variations of this ener y; these electrical elements are connected in series with opposite polarity so that their combined output voltage is equal to the difference between the individual output voltages of these electrical elements.

As stated above, the electrical elements used for an electrical arrangement according to my present invention are chosen so as to have logarithmic voltage characteristics 50 that their individual output voltages er and 62 vary proportionally to the logarithm of the activating energy 2. Furthermore, these electrical elements have to be connected in series with opposite polarity so that their combined output voltage E is equal to the dilference of their individual output voltages e1 and e2.

In accordance with a further preferred embodiment of m present invention, I provide means combined with one or both of the electrical elements for varying the relative intensity of their activation b the above mentioned'source of activating energy. By providing such means the electrical elements are activated from the same source of energy 1 by different fractions in and kg of this energy.

As stipulated above, the individual output voltage of one of the electrical elements is e1=c log km and the individual output voltage of the other element is 62:12 lo kzi, wherein c is a constant coefiicient. Furthermore, from above it follows that the combined output voltage E of both elements connected in series, i. e. of the entire arrangement is Thus, it is evident that the combined output Voltage E of the entire arrangement depends only on the general constant c and on the proportion ki/lcz, but that this combined output voltage does not depend on the intensity of the activating energy, if both electrical elements are activated by the same source of activating energy. Thus, the combined output voltage E will remain constant even if the intensity of the activating energy varies.

While no electrical elements are known which have a logarithmic voltage characteristic of the above defined type down to vanishing activation, i. e. down to i=0, nevertheless, for practical purposes, it is suflicient to use in electrical arrangements of the type here proposed electrical elements whose voltages vary with the intensity variations of the activating energy 2' in logarithmic proportion over a relatively large range.

Among the various types of electrical elements that might be used, photoelectric elements, particularly selenium barrier layer cells are very well adapted for the purposes of my present invention. Furthermore, I have found that certain contact rectifier elements, as for instance copperoxide and germanium-alloy contact rectifiers give very satisfactory results.

The novel features which I consider as characteristic for my invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a schematic section through a selenium barrier layer cell of known type;

Fig. 2 is a diagram showing the logarithmic oltage characteristic of a cell of the type shown in Fig. 1;

Fig. 3 is a schematic view of an electrical arrangement according to my present invention, embodying photoelectric elements;

Fig. 4 is a circuit diagram of an electrical arrangement of the type shown in Fig. 3 combined with an electrical measuring instrument;

Fig. is a circuit diagram of an arrangement similar to the one shown in Fig. 4 combined with a measuring instrument of different type;

Fig. 6 is a perspective view of a modified. embodiment of the electrical arrangement shown in Fig. 3;

Fig. '7 is a circuit diagram of an electrical arrangement according to my present invention, embodying contact rectifier elements; and

Fig. 8 is a circuit diagram of a modified electrical arrangement similar to the electrical arrangement shown in Fig. 7.

The selenium barrier layer cell shown in Fig. 1

consists of a selenium barrier layer It deposited on a metal base II and covered by a transparent conducting front electrode I2. The short-circuit current from such a cell rises, as well-known, in nearly linear proportion with the intensity of its illumination by the light source I3 schematically shown in Fig. 1.

However, from observation as well as from the theory of barrier layers, it is known that the open-circuit output voltage of .such a cell rises, over several decades of light intensity, in exactly logarithmic proportion with the intensity of the illumination, as shown in Fig. 2.

In the electrical arrangement according to my present invention shown in Fig. 3, two at least substantially equal photoelectric elements I5 and If of the type shown in Fig. l are connected in series with opposite polarity and illuminated by the same light source II. If both these elements I5 and I6 would receive an equal amount of light, their individual output voltages er and 22 would be equal, and, accordingly, their combined output voltage E would be equal to zero.

If, however, the intensity of their illumination is made different, e. g. by reduction of the amount of light reaching one of the elements-for instance by insertion of a light absorbing translucent plate I8 in front of cell I5 in the path of the light rays emitted by light source I'I-then the combined output voltage E of both elements j."

I5 and I6 will be proportional to the ratio of their illuminations, i. e. will be proportional to the density of the light absorbing plate I8.

I have found that with an arrangement of this type I am able to obtain, across the output terminals I9 and of the combined photoelectric elements I5 and I6, a combined output voltage E which depends only on the light absorption of plate I8, i. e. on the density of this plate, and is over a wide range substantially independent of intensity variations of the light source H. In order to obtain a combined output voltage E that is exactly proportional to the density of the plate I8 and fully independent of variations of the intensity of the light source II, it is necessary that both photoelectric elements I5 and I6 receive enough illumination so as to operate in the range of logarithmic law and that the impedance of the voltage measuring device is very high compared with that of the photoelectric elements under operating conditions.

A suitable voltage measuring device, i. e. a measuring device whose impedance is very high compared with that of the photoelectric elements and which therefore can very well be used for measuring the combined output voltage of the arrangement shown in Fig. 3, is a measuring circuit of the type shown in Fig. 4. In this measuring circuit, the combined output voltage E is fed to the negatively biased control grid 2| of an amplifier tube 22 and the corresponding change in plate current is measured with a current meter 23 of known type.

A modification of a circuit of this type is shown in 5: In this modification the two individual output voltages er and c2 are fed to grids 24 and 25, respectively, of an initially balanced pair of amplifier tubes 26 and 2?, respectively, and the resulting unbalance in plate currents is measured by a current meter 28; the current indicated by this meter 28 will be proportional to the ratio of the illuminations of the two photoelectric ele ments I5 and I6 but not dependent on the intensity of the light emitted by the light source II.

An arrangement of the above described type is very well adapted for comparing and measuring the light absorption of various materials since it is unaffected by intensity variations of the light emitted by the light source illuminating these materials.

Furthermore, an arrangement of the type shown in Fig. 3 provided with an adjustable light absorbing member, e. g. a movable calibrated gray Wedge in front of one of the photoelectric elements, might very Well be used as an adjustable yet constant source of small voltages, as may be required in various fields of science, such as the measurement of small contact potentials.

Still another application of an arrangement of the type described above is its use as constant grid bias for amplifier tubes: In such a case both photoelectric elements are preferably combined in a single unit as shown in Fig. 6. This unit consists of a common metal base 29, two selenium barrier layers 30 and 3 I and two transparent conducting front electrodes 32 and 33 covering the barrier layers 30 and 3I, respectively. In accordance with the present invention, these barrier layers 30 and 3I are connected in series with opposite polarity. The output terminals 34 and 35 are connected only to the two front electrodes 32 and 33, respectively.

The combined output voltage of such a unit is determined only by the opacity of the light absorbing member 35 covering the front electrode 33. Since above a certain minimum illumination the combined output voltage E across the terminals 3 3 and 35 is entirely independent of the intensity of the light emitted by the light source illuminating the front electrodes 32 and 33, it follows that even a light source emitting a light beam with considerable intensity variations will produce substantially constant combined output voltage E across the terminals 34 and 35. Thus, an incandescent lamp fed by alternating current will be adequate as light source for illuminating the electrodes.

Therefore, if an arrangement of this type is used as a source of constant grid bias for amplifier tubes in electronic equipments, various light sources usually available in such equipments, such as the dial light, may serve as light source for illuminating the photoelectric elements; I have found that in some cases even the glow of the cathode heating means of the amplifier tube to be biased is strong enough to serve as light source for illuminating and thus activating the photoelectric elements which by such activation will supply the constant grid bias for the tube as explained above.

It is Well known that the output voltage of photoelectric elements of the above described type is independent of their surface areas. Thus, the individual output voltages er and e: of the photoelectric elements I5 and I6 and their comitali bined output voltage E are independent of the surface area of these elements.

However, it is also known that the source impedance of photoelectric elements is inversely proportional to their areas. Therefore, the surface areas of the photoelectric elements I5 and I6 should be made so large that their source impedance is low in comparison with incidental loads, such as leakage and ionic grid currents in the amplifier tube.

In order to provide larger constant voltages than are obtainable from a single pair of photoelectric elements, I propose to connect two or more-pairs of opposing photoelements in series, in a manner familiar from other voltage sources.

Another group of elements with logarithmic voltage characteristics comprises certain nonlinear conductors such as copper-oxide and germanium-alloy contact rectifiers. The output voltage, i. e. voltage drop on such elements rises in certain ranges of both their conducting and insulating direction in strictly logarithmic proportion with the density of the current flowing through their barrier layer. This logarithmic proportionality holds true, for example, in certain germanium-alloy contact rectifiers over a range of at least five decades of current.

Thus, by using such rectifier elements, 9. g. by incorporating them in a bridge circuit as shown in Fig. '7, it is possible to obtain a combined output voltage E which remains constant despite variations of the activating current. In this circuit, the two contact rectifiers 38 and 39 are arranged in series with opposite polarity; they are connected on the one hand with the inconstant, i. e. varying direct current source 31 and on the other hand with the output terminals 40 and 4 I.

Two resistor elements 42 and 43 are included in the conductors 44 and 45 connecting the current source 31 with the rectifier elements 38 and 39, respectively. These resistor elements 42 and 43 have very large resistances compared with the resistances of the rectifier elements 38 and 39 under operating conditions.

In order to obtain a combined output voltage E across the terminals 40 and 4|, it is necessary either to make the areas of the rectifier elements 38 and 39 equal and the resistances of the resistor elements 42 and 43 very different from each other, or to make the resistances of the resistor elements 42 and 43 equal and the areas of the rectifier elements 38 and 39 very different from each other; of course, it is possible to obtain the desired results also by making the resistances of both the resistor elements 42 and 43 and the areas of the rectifier elements 38 and 39 different from each other.

It is evident that it is possible to vary the combined output voltage E across terminals 40 and 4| by making one of the resistors 42 and 43 or both of them variable; thus, it is possible to vary and adjust the obtained combined output voltage E within wide limits.

The resulting combined output voltage E of such an arrangement across the output terminals 40 and 4| depends again, as in all other above described arrangements, exclusively on the ratio of the currents through the resistor elements 42 and 43 and not on variations of the current supplied by the current source 31; this holds true so long as the resistances of the resistor elements 42 and 43 are substantially larger than the resistances of the rectifier elements 38 and 39.

With an arrangement of the type shown in Fig. 7, only a relatively small combined output voltage E is obtainable since the resistances of the resistor elements 42 and 43 are relatively high. In order to obtain a larger output voltage E, it is therefore advantageous to reduce somewhat the resistances of the resistor elements 42 and 43.

In this event, the output voltage E will no longer be fully independent of intensity variations of the current supplied by the current source 31 but slightly vary in accordance with variations of the same as usual in bridge circuits composed of ohmic resistances. To compensate for such variations, I propose to insert, as shown in Fig. 8,. an additional resistor element 46 in series with the rectifier element 38 carrying less current density. The resistance of this additional resistor element 46 can be chosen so that the combined output voltage E is again independent of the intensity variations of the activating current over a substantial range of the latter.

Arrangements of the type shown in Figs. '7 and 3 might very well be used as sources of constant voltage; however, they might also be used for testing and measuring purposes by including into the same the electrical element to be tested or measured, or by substituting for one of the resistor elements 42 or 43 a resistor element the characteristics of which have to be determined.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of electrical arrangements diflering from the types described above.

While I have illustrated and described the in vention as embodied in electrical arrangements used as constant voltage sources, I do not intend to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of my invention.

Without further analysis, the foregoing will so fully reveal the gist of my invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

What I claim as new and desire to secure by Letters Patent is:

1. An electrical arrangement comprising in combination a source of activating energy; two electrical elements, each being activated by said source of activating energy and having a logarithmic voltage characteristic so as to yield during activation by said source of activating energy an individual output voltage the voltage variations of which in case of intensity variations of said activating energy are in logarithmic proportion with said intensity variations; said electrical elements being connected in series with opposite polarity so that their combined output voltage at their output terminals is equal to the difierence between said individual output voltages of said electrical elements; and an electrical load circuit having an impedance which is substantially higher than the impedance of said electrical elements during activation by said source of activating energy, said electrical load circuit being connected to said output terminals of said electrical elements.

2. An electrical arrangement comprising in combination a source of activating energy; two

assigned electrical elements, each being activated by said source of activating energy and having a logarithmic voltage characteristic so as to yield during activation by said source of activating energy an individual output voltage the voltage variations ofwhich in case of intensity variations of said activating energy are in logarithmic proportion with said intensity variations; said electrical elements being connected in series with opposite polarity so that their combined output voltage at their output terminals is equal to the difference between said individual output voltages of said electrical elements; and an electrical voltage measuring instrument having an impedance which is substantially higher than the impedance of said electrical elements, said electrical voltage measuring instrument being connected with said output terminals of said electrical elements.

3-. An electrical arrangement comprising in combination a light source; two photoelectric elements, each being activated by said light source and having a logarithmic voltage characteristic so as to yield during activation by said light source an individual output voltage the voltage variations of which in case of intensity variations of the light emitted by said light source are in logarithmic proportion with said intensity variations; said photoelectric elements being connected in series with opposite polarity so that their combined output voltage is equal tothe difference between said individual output voltages of said photoelectric elements; and an electrical load circuit having an impedance which is substantially higher than the impedance of said photoelectric elements during activation by said light source, said electrical load circuit being connected to the output terminals of said photoelectric elements.

4. An electrical arrangement comprising in combination a light source; two photoelectric elements, each being activated by said light source and having a. logarithmic voltage characteristic so as to yield during activation by said light source an individual output voltage the voltage variations of which in case of intensity variations of the light emitted by said light source are in logarithmic proportion with said intensity variations; said photoelectric elements being connected in series with opposite polarity so that their combined output voltage is equal to the difference between said individual output voltages of said photoelectric elements; light absorbing means arranged between said light source and one of said photoelectric elements in the path of the light rays emitted by said light source so as to decrease the amount of light reaching said photoelectric element and the degree of activation of said photoelectric element by said light source and an electrical load circuit having an impedance which is substantially higher than the impedance of said photoelectric elements during activation by said light source, said electrical Load circuit being connected to the output terminals of said photoelectric elements.

5. An electrical arrangement comprising in combination a light source; two photoelectric elements, each being activated by said light source and having a logarithmic voltage characteristic so as to yield during activation by said light source an individual output voltage the voltage variations of which in case of intensity variations of the light emitted by said light source are in logarithmic proportion with said intensity variations; said photoelectric elements being con- &

nected in series with opposite polarity so that of activation of said photoelectric element by saidlight source and an electrical load circuit having an impedance which is substantially higher than the impedance of said photoelectric elements during activation by said light source, said electrical load circuit being connected to the output terminals of said photoelectric elements.

6. An electrical arrangement comprising in combination alight source; two photoelectric elements, each being activated by said light source and having a logarithmic voltage characteristic so as to yield during activation by said light source an individual output voltage the voltage variations of which in case of intensity variations of the light emitted by said light source are in logarithmic proportion with said intensity variations; said photoelectric elements being connected in series with opposite polarity so that their combined output voltage is equal to the difierence between said individual output voltages of said photoelectric elements; an adjustable gray wedge arranged between said light source and one of said photoelectric elements and an electrical load circuit having an impedance which is substantially higher than the impedance ofi said photoelectric elements during activation by said light source, said electrical load circuit being connected to the output terminals of said photoelectric elements.

7. An electrical arrangement comprising in combination a light source; two photoelectric elements, each being activated by said light source and having a logarithmic voltage characteristic so as to yield during activation by said light source an individual output voltage the voltage variations of which in case of intensity variations of the light emitted by said light source are in logarithmic proportion with said intensity variations; said photoelectric elements being con"- nected in series with opposite polarity so that their combined output voltage at their output terminals is equal to the difference between said individual output voltages of said photoelectric elements; light absorbing means arranged between said light source and one of said photoelectric elements in the path of the light rays emitted by saidlight source so as to decrease the amount of light reaching said photoelectric element and the degree of activation of said photoelectric element by said light source; and an electrical voltage measuring instrument having an impedance which is substantially higher than the impedance of said photoelectric elements combined, said electrical voltage measuring instrument being connected With said output terminal of said photographic elements.

8. An electrical arrangement comprising in combination a source of electrical current; two electrical contact rectifier elements each being connected with said source of electrical current soas to be activated by the same and having a logarithmic voltage characteristic soas to yield during activation by said source of electrical current an individual output voltage the voltage variations of which in case of intensity variations of said electrical current are in logarithmic proportion with said intensity variations; said electrical contact rectifier elements being connected in series with opposite polarity so that their combined output voltage is equal to the diiference between said individual output voltages of said electrical contact rectifier elements; and an electrical load circuit having an impedance which is substantially higher than the impedance of said electrical contact rectifier elements during activation by said source of electric current, said electrical load circuit being connected to the output terminals of said electrical contact rectifier elements.

9. An electrical arrangement comprising an electrical circuit; a source of electrical current in said circuit; two electrical contact rectifier elements having a logarithmic voltage characteristic; electrical conductors connecting each of said electrical contact rectifier elements with said source of electrical current so that said electrical contact rectifier elements are activated by said source of electrical current and yield each during such activation an individual output voltage the voltage variations of which in case of intensity variations of said electrical current are in logarithmic proportion with 'said intensity variations; said electrical contact rectifier elements being connected in series with opposite polarity so that their combined output voltage is equal to the difierence between said individual output voltages of said electrical contact rectifier elements; and an electrical load circuit having an impedance which is substantially higher than the impedance of said electrical contact rectifier elements during activation by said source of electric current, said electrical load circuit being connected to the output terminals of said electrical contact rectifier elements.

10. An electrical arrangement comprising in combination a source of electrical current; two electrical contact rectifier elements each being connected with said source of electrical current so as to be activated by the same and having a logarithmic voltage characteristic so as to yield during activation by said source of electrical current an individual output voltage the voltage variations of which in case of intensity variations of said electrical current are in logarithmic proportion with said intensity variations; said electrical contact rectifier elements being connected in series with opposite porality so that their combined output voltage is equal to the difference between said individual output voltages of said electrical contact rectifier elements; two electrical resistor elements having a resistance being substantially larger than the resistance of said electrical contact rectifier elements, each of said resistor elements being included in one of the connections between said source of electric current and said electrical contact rectifier elements; and an electrical load circuit having an impedance which is substantially higher than the impedance of said electrical contact rectifier elements during activation by said source of electric current, said electrical load circuit being connected to the output terminals of said electrical contact rectifier elements.

11. An electrical arrangement comprising in combination a source of electrical current; two electrical contact rectifier elements each being connected with said source of electrical current so as to be activated by the same and having a logarithmic voltage characteristic so as to yield during activation by said source of electrical current an individual output voltage the voltage variations of which in case of intensity variations of said electrical current are in logarithmic proportion with said intensity variations; said electrical contact rectifier elements being connected in series with opposite polarity so that their combined output voltage is equal to the difference between said individual output voltages of said electrical contact rectifier elements; a variable resistor element included in the connection between said source of electrical current and one of said electrical contact rectifier elements, said variable resistor element having a resistance being substantially larger than the resistance of the contact rectifier element with which it is connected; and an electrical load circuit having an impedance which is substantially higher than the impedance of said electrical contact rectifier elements during activation by said source of electric current, said electrical load circuit being connected to the output terminals of said electrical contact rectifier elements.

12. An electrical arrangement comprising an electrical bridge circuit; a source of electrical current in said bridge circuit; two electrical contact rectifier elements having a logarithmic voltage characteristic; electrical conductors connecting each of said electrical contact rectifier elements with said source of electrical current so that said electrical contact rectifier elements are activated by said source of electrical current and yield each during such activation an individual output voltage the voltage variations of which in case of intensity variations of said electrical current are in logarithmic proportion with said intensity variations; said electrical contact rectifier elements being connected in series with opposite polarity so that their combined output voltage is equal to the difference between said individual output voltage of said electrical contact rectifier elements; two electrical resistor elements, said resistor elements being. included in said electrical conductors between said source of electric current and said electrical contact rectifier elements; an additional electrical resistor element being included in one of said conductors in series with one of said electrical contact rectifier elements; and an electrical load circuit having an impedance which is substantially higher than the impedance of said electrical contact rectifier elements during activation by said source of electric current, said electrical load circuit being connected to the output terminals of said electrical contact rectifier elements.

13. An electrical arrangement comprising an electrical circuit; a source of electrical current in said circuit; two electrical contact rectifier elements having a logarithmic voltage characteristic; electrical conductors connecting each of said electrical contact rectifier elements with said source of electrical current so that said electrical contact rectifier elements are activated by said source of electrical current and yield each during such activation an individual output voltage the voltage variations of which in case of intensity variations of said electrical current are in logarithmic proportion with said intensity variations; said electrical contact rectifier elements being connected in series with opposite polarity so that their combined output voltage is equal to the difierence between said individual output voltages of said electrical contact rectifier elements; two electrical resistor elements at least one of which is variable, said resistor elements being included in said electrical conductors between said source of electric current and said I 1 electrical contact rectifier elements; and an electrical load circuit having an impedance which is substantially higher than the impedances of said electrical contact rectifier elements during activation by said source of electric current, said electrical load circuit being connected to the output terminals of said electrical contact rectifier elements.

HEINZ E. KALLMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,337,905 Sheldon Dec. 1, 1931 Number Number Name Date W Wilson June 19; 1934 Sheldon et a1. Aiig. 31, 1934 Goodwin Mar. 16, 1937 Ladrich July 5, 1933 Lane Jan. 2, 1940 Victdren Feb. 13, 1940 Tolmari Mar. 4, 1941 Gilbert Apr. 22, 1941 Mott-Smith Dec. 8, 1942 FOREIGN PATENTS Country Date Great Britain July 6, 1933 France Mar. 14, 1932 

